US2007026833A1PendingUtilityA1
Method, apparatus and computer program product providing widely linear interference cancellation for multi-carrier systems
Est. expiryAug 1, 2025(expired)· nominal 20-yr term from priority
Inventors:Kiran Kumar Kuchi
H04L 27/26524H04L 27/2647H04L 25/03299
44
PatentIndex Score
0
Cited by
0
References
0
Claims
Abstract
A method is provided. The method includes: receiving a multi-carrier signal that includes a plurality of subcarriers; and performing widely linear (WL) processing on the received signal.
Claims
exact text as granted — not AI-modified1 . A method comprising:
receiving a multi-carrier signal comprising a plurality of subcarriers; and performing widely linear (WL) processing on the received signal.
2 . The method of claim 1 , wherein the multi-carrier signal comprises an orthogonal frequency division multiplexed (OFDM) signal.
3 . The method of claim 1 , wherein the received multi-carrier signal comprises a signal modulated using conjugate symmetric modulation.
4 . The method of claim 3 , wherein a time domain received signal in baseband form is denoted as:
y
k
=h
k
⊕s
k
+n
k
and wherein in-phase and quadrature parts of the received signal are collected and stacked in vector format as:
[
ℜ
y
k
??
y
k
]
=
[
ℜ
h
k
??
h
k
]
⊗
s
k
+
[
ℜ
n
k
??
n
k
]
which has a vector form:
{tilde over (y)} k ={tilde over (h)} k ⊕s k +ñ k .
5 . The method of claim 4 , wherein a frequency domain received signal is denoted as:
{tilde over (y)} ( f k )= {tilde over (h)} ( f k ) x ( f k )+ ñ ( f k ),
wherein elements of the denoted frequency domain received signal are complex valued and exhibit conjugate symmetry, wherein an information carrying symbols pair [x(f k ),x*(N−f k )] is combined using an un-biased minimum mean-squared error (MMSE) scheme such that:
z
(
f
k
)
=
1
2
h
~
†
(
f
k
)
R
n
~
n
~
-
1
(
f
k
)
[
y
~
(
f
k
)
+
y
~
*
(
N
-
f
k
)
]
for
k
=
1
,
…
,
N
2
-
1
where MMSE weights are applied after combing conjugate symmetric parts.
6 . The method of claim 3 , wherein WL filtering is applied to complex and complex-conjugate replicas such that:
y ( f k )= h ( f k ) x ( f k )+ n ( f k )
where
y ( f k )≅[ y ( f k ), y *( N−f k )]′, h ( f k )≅[ h ( f k ), h *( N−f k )]′, n ( f k )≅[ n ( f k ), n *( N−f k )]′.
7 . The method of claim 6 , wherein a conjugate symmetric symbol pair [x(f k ), x*(N−f k )] is combined such that:
z
_
(
f
k
)
=
1
2
h
~
†
(
f
k
)
R
n
~
n
~
-
1
(
f
k
)
y
_
(
f
k
)
for
k
=
1
,
…
,
N
2
-
1
,
where R n n −1 (f k ) denotes a WL noise correlation matrix and z (f k ) denotes a scalar decision variable used to generate bit wise soft decisions.
8 . The method of claim 1 , wherein the received multi-carrier signal comprises a signal modulated using Pulse Amplitude Modulation (PAM).
9 . The method of claim 8 , wherein the WL processing comprises a Discrete Fourier Transform (DFT), wherein an output of the DFT comprises:
y ( f k )= h ( f k ) a ( f k )+ n ( f k ),
wherein in-phase and quadrature parts of the received signal are collected such that:
[
ℜ
y
(
f
k
)
??
y
(
f
k
)
]
=
[
ℜ
h
(
f
k
)
??
h
(
f
k
)
]
s
k
+
[
ℜ
n
(
f
k
)
??
n
(
f
k
)
]
which has a compact vector form:
{hacek over (y)} ( f k )= {hacek over (h)} ( f k ) a ( f k )+ {hacek over (n)} ( f k ).
10 . The method of claim 9 , wherein linear minimum mean squared error (LMMSE) symbol estimates are provided such that:
{hacek over (z)} ( f k )= {hacek over (h)} †( f k ) R {hacek over (n)}{hacek over (n)} −1 ( f k ) {hacek over (y)} ( f k ).
11 . The method of claim 1 , wherein the received multi-carrier signal comprises a signal modulated using Quadrature Amplitude Modulation (QAM).
12 . The method of claim 11 , wherein the WL processing comprises a Discrete Fourier Transform (DFT), wherein a frequency domain output of the DFT comprises:
y ( f k )= h ( f k ) b ( f k )+ n ( f k ),
wherein in-phase and quadrature parts of the received signal in a frequency domain are collected such that:
[
y
I
(
f
k
)
y
Q
(
f
k
)
]
=
[
h
I
(
f
k
)
-
h
Q
(
f
k
)
h
Q
(
f
k
)
h
I
(
f
k
)
]
[
b
I
(
f
k
)
b
Q
(
f
k
)
]
+
[
n
I
(
f
k
)
n
Q
(
f
k
)
]
which has a vector-matrix form:
y ( f k )= H ( f k ) b ( f k )+ n ( f k ).
13 . The method of claim 12 , wherein QAM symbols are recovered using a ML/MAP decoder that minimizes a distance term, wherein the distance term comprises:
d ( f k )= e ( f k ) R nn −1 ( f k ) e ( f k ),
wherein the candidate symbol e (f k ) comprises:
e ( f k )= y ( f k )− H ( f k ) {circumflex over (b)} ( f k )
14 . The method of claim 1 , wherein performing widely linear (WL) processing on the received signal comprises:
splitting the received signal into a real part and an imaginary part; applying a Discrete Fourier Transform (DFT) to the real part and the imaginary part, wherein outputs of the DFT comprise an in-phase branch signal and a quadrature branch signal; applying a whitening filter to the in-phase branch signal and the quadrature branch signal; and demodulating an output of the whitening filter.
15 . The method of claim 14 , wherein the whitening filter comprises a pre-whitening filter utilizing Choleski factorization of a noise correlation matrix.
16 . The method of claim 1 , wherein performing widely linear (WL) processing on the received signal comprises:
applying a Discrete Fourier Transform (DFT) to the received signal; splitting an output of the DFT into a real part and an imaginary part; applying a whitening filter to the real part and the imaginary part; and demodulating an output of the whitening filter.
17 . The method of claim 1 , wherein performing widely linear (WL) processing on the received signal comprises:
applying a Discrete Fourier Transform (DFT) to the received signal, wherein outputs of the DFT comprise a complex part of the signal and a complex-conjugate part of the signal; applying a conjugate symmetry operation to the complex part and the complex-conjugate part; applying a whitening filter to outputs of the conjugate symmetry operation; and demodulating an output of the whitening filter.
18 . The method of claim 1 , wherein performing widely linear (WL) processing on the received signal comprises:
applying a Discrete Fourier Transform (DFT) to the received signal, splitting an output of the DFT into a complex part of the signal and a complex-conjugate part of the signal; applying a conjugate symmetry operation to the complex part and the complex-conjugate part; applying a whitening filter to outputs of the conjugate symmetry operation; and demodulating an output of the whitening filter.
19 . The method of claim 1 , wherein the multi-carrier signal comprises one of an Ultra-Wideband (UWB) signal or a Wireless Local Area Network (WLAN) signal.
20 . A computer program product comprising program instructions embodied on a tangible computer-readable medium, execution of the program instructions resulting in operations comprising:
inputting a received multi-carrier signal comprising a plurality of subcarriers; and performing widely linear (WL) processing on the received signal.
21 . The computer program product of claim 20 , wherein the multi-carrier signal comprises a signal modulated using conjugate symmetric modulation, wherein a time domain received signal in baseband form is denoted as:
y k =h k ⊕s k +n k ,
wherein in-phase and quadrature parts of the received signal are collected and stacked in vector format as:
[
ℜ
y
k
??
y
k
]
=
[
ℜ
h
k
??
h
k
]
⊗
s
k
+
[
ℜ
n
k
??
n
k
]
which has a vector form:
{tilde over (y)} k ={tilde over (h)} k ⊕s k +ñ k .
22 . The computer program product of claim 21 , wherein a frequency domain received signal is denoted as:
{tilde over (y)} ( f k )= {tilde over (h)} ( f k ) x ( f k )+ ñ ( f k ),
wherein elements of the denoted frequency domain received signal are complex valued and exhibit conjugate symmetry, wherein an information carrying symbols pair [x(f k ),x*(N−f k )] is combined using an un-biased minimum mean-squared error (MMSE) scheme such that:
z
(
f
k
)
=
1
2
h
~
†
(
f
k
)
R
n
~
n
~
-
1
(
f
k
)
[
y
~
(
f
k
)
+
y
~
*
(
N
-
f
k
)
]
for
k
=
1
,
…
,
N
2
-
1
where MMSE weights are applied after combing conjugate symmetric parts.
23 . The computer program product of claim 20 , wherein the multi-carrier signal comprises a signal modulated using conjugate symmetric modulation, wherein WL filtering is applied to complex and complex-conjugate replicas such that:
y ( f k )= h ( f k ) x ( f k )+ n ( f k )
where
y ( f k )≅[ y ( f k ), y *( N−f k )]′, h ( f k )≅[ h ( f k ), h *( N−f k )]′, n ( f k )≅[ n ( f k ), n *( N−f k )]′.
24 . The computer program product of claim 23 , wherein a conjugate symmetric symbol pair [x(f k ), x*(N−f k )] is combined such that:
z
_
(
f
k
)
=
1
2
h
_
†
(
f
k
)
R
n
_
n
_
-
1
(
f
k
)
y
_
(
f
k
)
for
k
=
1
,
…
,
N
2
-
1
,
where R n n −1 (f k ) denotes a WL noise correlation matrix and z (f k ) denotes a scalar decision variable used to generate bit wise soft decisions.
25 . The computer program product of claim 20 , wherein the multi-carrier signal comprises a signal modulated using Pulse Amplitude Modulation (PAM), wherein the WL processing comprises a Discrete Fourier Transform (DFT), wherein an output of the DFT comprises:
y ( f k )= h ( f k ) a ( f k )+ n ( f k ),
wherein in-phase and quadrature parts of the received signal are collected such that:
[
ℜ
y
(
f
k
)
??
y
(
f
k
)
]
=
[
ℜ
h
(
f
k
)
??
h
(
f
k
)
]
s
k
+
[
ℜ
n
(
f
k
)
??
n
(
f
k
)
]
which has a compact vector form:
{hacek over (y)} ( f k )= {hacek over (h)} ( f k ) a ( f k )+ {hacek over (n)} ( f k ).
26 . The computer program product of claim 25 , wherein linear minimum mean squared error (LMMSE) symbol estimates are provided such that:
{hacek over (z)} ( f k )= {hacek over (h)} †( f k ) R {hacek over (n)}{hacek over (n)} −1 ( f k ) {hacek over (y)} ( f k ).
27 . The computer program product of claim 20 , wherein the multi-carrier signal comprises a signal modulated using Quadrature Amplitude Modulation (QAM), wherein the WL processing comprises a Discrete Fourier Transform (DFT), wherein a frequency domain output of the DFT comprises:
y ( f k )= h ( f k ) b ( f k )+ n ( f k ),
wherein in-phase and quadrature parts of the received signal in a frequency domain are collected such that:
[
y
I
(
f
k
)
y
Q
(
f
k
)
]
=
[
h
I
(
f
k
)
-
h
Q
(
f
k
)
h
Q
(
f
k
)
h
I
(
f
k
)
]
[
b
I
(
f
k
)
b
Q
(
f
k
)
]
+
[
n
I
(
f
k
)
n
Q
(
f
k
)
]
which has a vector-matrix form:
y ( f k )= H ( f k ) b ( f k )+ n ( f k ).
28 . The computer program product of claim 27 , wherein QAM symbols are recovered using a ML/MAP decoder that minimizes a distance term, wherein the distance term comprises:
d ( f k )= e ( f k ) R nn −1 ( f k ) e ( f k ),
wherein the candidate symbol e (f k ) comprises:
e ( f k )= y ( f k )− H ( f k ) {circumflex over (b)} ( f k ).
29 . An electronic device comprising:
a multi-carrier radio frequency receiver having an input for coupling to at least one antenna; a signal processing block coupled to an output of the receiver, wherein the signal processing block comprises a widely linear (WL) signal processing unit operable to demodulate a received multi-carrier signal; and a decoder having an input coupled to an output of the signal processing block.
30 . The electronic device of claim 29 , wherein the signal processing block comprises:
a Discrete Fourier Transform (DFT) having an input coupled to an output of the receiver; a whitening filter having an input coupled to an output of the DFT; and a demodulator having an input coupled to an output of the whitening filter and an output coupled to an input of the decoder.
31 . The electronic device of claim 29 , wherein the multi-carrier signal comprises a signal modulated using conjugate symmetric modulation, wherein a time domain received signal in baseband form is denoted as:
y k =h k ⊕s k +n k ,
wherein in-phase and quadrature parts of the received signal (are collected and stacked in vector format as:
[
ℜ
y
k
??
y
k
]
=
[
ℜ
h
k
??
h
k
]
⊗
s
k
+
[
ℜ
n
k
??
n
k
]
which has a vector form:
{tilde over (y)} k ={tilde over (h)} k ⊕s k +ñ k .
32 . The electronic device of claim 29 , wherein the multi-carrier signal comprises a signal modulated using Pulse Amplitude Modulation (PAM), wherein the WL signal processing unit comprises a Discrete Fourier Transform (DFT), wherein an output of the DFT comprises:
y ( f k )= h ( f k ) a ( f k )+ n ( f k ),
wherein in-phase and quadrature parts of the received signal are collected such that:
[
ℜ
y
(
f
k
)
??
y
(
f
k
)
]
=
[
ℜ
h
(
f
k
)
??
h
(
f
k
)
]
s
k
+
[
ℜ
n
(
f
k
)
??
n
(
f
k
)
]
which has a compact vector form:
{hacek over (y)} ( f k )= {hacek over (h)} ( f k ) a ( f k )+ {hacek over (n)} ( f k ).
33 . The electronic device of claim 29 , wherein the multi-carrier signal comprises a signal modulated using Quadrature Amplitude Modulation (QAM), wherein the WL signal processing unit comprises a Discrete Fourier Transform (DFT), wherein a frequency domain output of the DFT comprises:
y ( f k )= h ( f k ) b ( f k )+ n ( f k ),
wherein in-phase and quadrature parts of the received signal in a frequency domain are collected such that:
[
y
I
(
f
k
)
y
Q
(
f
k
)
]
=
[
h
I
(
f
k
)
-
h
Q
(
f
k
)
h
Q
(
f
k
)
h
I
(
f
k
)
]
[
b
I
(
f
k
)
b
Q
(
f
k
)
]
+
[
n
I
(
f
k
)
n
Q
(
f
k
)
]
which has a vector-matrix form:
y ( f k )= H ( f k ) b ( f k )+ n ( f k ).
34 . An integrated circuit comprising
a multi-carrier radio frequency receiver having an input for coupling to at least one antenna; a signal processing block coupled to an output of the receiver, wherein the signal processing block comprises a widely linear (WL) signal processing unit operable to demodulate a received multi-carrier signal; and a decoder having an input coupled to an output of the signal processing block.
35 . The integrated circuit of claim 34 , wherein the signal processing block comprises:
a Discrete Fourier Transform (DFT) having an input coupled to an output of the receiver; a whitening filter having an input coupled to an output of the DFT; and a demodulator having an input coupled to an output of the whitening filter and an output coupled to an input of the decoder.Join the waitlist — get patent alerts
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